1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device used in the fabrication of a pressure sensor, acceleration sensor, vibration sensor or the like, and particularly to a method for fabricating a mono-crystalline silicon diaphragm or pressure sensor into various shapes such as a circle, triangle, spiral or the like using a porous silicon, regardless of the type of substrate, and a crystalline orientation of the substrate.
2. Description of the Prior Art
Conventionally, a mono-crystalline silicon diaphragm is fabricated by either isotropically or anisotropically etching the backside of the substrate.
The isotropic etching process has the advantage in that the diaphragm may be fabricated into various shapes, but it cannot be used in practice as it creates undesirable side etch phenomenon.
On the other hand, when the anisotropic etching process is used in the fabrication the diaphragm, undesirable side etch phenomenon can be prevented because the (111) crystalline plane of the substrate, which is not etched, lies in the side surface thereof. However, the anisotropic etching process still has the disadvantage in that it cannot be fabricated into a quadrilateral shape. This is because the shape of the diaphragm is defined according to the crystalline orientation of the substrate.